. Nature and development of plants. Botany. DEVELOPMENT OF PLANTS 437 The buckwheat order, Polygonales, containing such familiar weeds as the sorrel, dock {Rumex), and knotweed or smartweed (Polygonum), has perfect regular flowers with a distinct perianth. These characters also appear in the allied goosefoot order, Cheno- podiales, with its great array of common weeds, as the goosefoot (Chenopodium), orache (Atriplex), tumbleweed and pigweed. Fig. 304. Advanced type of the Chenopodiales: A, shoot of Melandry- num bearing flower with perianth differentiated into calyx, ca, and corolla, c. B, se
. Nature and development of plants. Botany. DEVELOPMENT OF PLANTS 437 The buckwheat order, Polygonales, containing such familiar weeds as the sorrel, dock {Rumex), and knotweed or smartweed (Polygonum), has perfect regular flowers with a distinct perianth. These characters also appear in the allied goosefoot order, Cheno- podiales, with its great array of common weeds, as the goosefoot (Chenopodium), orache (Atriplex), tumbleweed and pigweed. Fig. 304. Advanced type of the Chenopodiales: A, shoot of Melandry- num bearing flower with perianth differentiated into calyx, ca, and corolla, c. B, section of flower, showing the relation of calyx to corolla and the con- cealment of the nectar glands at the base of the ovary. Access to the corolla tube is guarded by an outgrowth on the petals, as shown in C, which, assisted by the styles or stamens, so effectually closes the mouth of the tube that only insects with long tongues can reach the honey. {Amaranthus). The flowers are arranged in loose clusters and are for the most part small and wind pollinated (Fig. 303). How- ever, it is noteworthy that some of the genera are adapted to insects, the calyx becoming larger and brightly colored and nectar glands are associated with it. In the higher members of the order, as in the purslane and pink families (which include the spring beauty, Claytonia), the perianth becomes differentiated into a calyx and showy corolla, and the flowers have become in a marked degree adapted to insect visitors (Fig. 304). These. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Curtis, Carlton Clarence, 1864-1945. New York, H. Holt
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